BEIRUT, July 18 (Reuters) - Syrian forces hit rebel positions across the capital on Wednesday, state media said, shortly after Damascus vowed to punish those responsible for a bomb attack which killed the defence minister and President Bashar al-Assad's brother-in-law. State news agency SANA said that armed forces had killed a large number of "terrorists" in the central neighbourhood of Midan and clashed in the district of Qaboun. Activists in neighbourhoods that have seen fighting over the past four days said that government troops and pro-government militias were flooding in to quash rebels. "There is a very heavy presence of security forces in the streets now," said Susan Ahmad, a resident of Barzeh where rebels have been hiding out. "Apart from Assad's forces, the streets are empty," she added. State television broadcast footage it said was filmed on Wednesday showing men in blue army fatigues ducking for cover and firing -- the first time official media has shown clashes in the heart of the capital. In a military statement read out on state television earlier on Wednesday, Syria said it would "chop any hand that harms national security."

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Hussein Ali Omar, 60, one of 11 Lebanese Shiite pilgrims that Syrian rebels have been holding for three months in Syria, hugs his mother, right, upon arrival at his house in the southern suburb of Beirut, Lebanon, 2012. Syrian rebels freed Omar on Saturday in a move aimed at easing cross-border tensions after a wave of abductions of Syrian citizens in Lebanon. The Shiite pilgrims were abducted May 22 after crossing into Syria from Turkey on their way to Lebanon. (AP Photo/Hussein Malla)

This image made from video and released by Shaam News Network and accessed Thursday, Aug. 23, 2012, purports to show the funeral of children in Daraya, near Damascus, Syria. Syrian troops backed by tanks and helicopters broke into a Damascus suburb on Thursday following two days of shelling and intense clashes as part of a widening offensive by President Bashar Assad's forces to seize control of parts of the capital and surrounding areas from rebel fighters, activists said. At least 15 people were killed in the offensive on Daraya, only a few miles (kilometers) southwest of Damascus. (AP Photo/Shaam News Network SNN via AP video)

Clashes between Assad supporters and opponents of the Syrian regime killed two people in Lebanon on Friday, the Associated Press reports. 17 people were injured.

The AP gives more context:

Syria was in virtual control of its smaller neighbor for many years, posting tens of thousands of troops in Lebanon, before withdrawing under pressure in 2005. Even without soldiers on the ground, Syria remains influential, and its civil war has stirred longstanding tensions that have lain under Lebanon's surface.

A Sunni gunman fires a gun during clashes that erupted between pro and anti-Syrian regime gunmen in the northern port city of Tripoli, Lebanon, Friday, Aug. 24, 2012. The latest round of fighting first erupted on Monday in northern Lebanon and at least 15 have been killed in Tripoli this week and more than 100 have been wounded in fighting that is a spillover from Syria's civil war. (AP Photo/Hussein Malla)

Syrian boy Musataf Alhafiz, 11, who fled his home with his family due to fighting between the Syrian army and the rebels, carries his brother Saif, 9 months, while he and others take refuge at the Bab Al-Salameh border crossing, in hopes of entering one of the refugee camps in Turkey, near the Syrian town of Azaz, Thursday, Aug. 23, 2012. Thousands of Syrians who have been displaced by the country's civil war are struggling to find safe shelter while shelling and airstrikes by government forces continue. (AP Photo/Muhammed Muheisen)

Lebanese commandos ride in an armored personnel carrier in preparation to enter the area of clashes between supporters and opponents of the Syrian regime, in the northern port city of Tripoli, Lebanon, Wednesday, Aug. 22, 2012. The civil war in Syria is affecting its fragile, tiny neighbor Lebanon in countless ways and has already spilled over into sectarian street clashes, kidnappings and general government paralysis.(AP Photo/Hussein Malla)

Activists say that Syrian security forces swept through two districts in Damascus on Wednesday, killing at least 31 suspected opposition fighters. The Associated Press reports that the army may have been targeting rebel teams that had been using the Nahr Eishah and Kfar Soussa neighborhoods to shell a nearby military airport.